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基本概念

• • 与数组很相似，但是Slices长度是可变的，操作方式与Python的list类型相似，例如新增一个元素。
• • 区别在于Slices通过指针指向数组，所以Slices是引用类型(Reference type)
• • 如果将slice复制给其他元素，则二者均是指向同一个底层数组
• • 对于函数传参时，也会指向统一底层数组
• • 切片可以由数组一部分进行截取• len返回的是长度• cap返回的是容量• 以下示例说明array的长度和容量是相同的，而对于slice，len是实际数组的长度，cap则大于len

package main import "fmt" func main() { var my_array [100]int my_slice := my_array[0:50] fmt.Printf("Slice len = %d\n", len(my_slice)) fmt.Printf("Slice cap = %d\n", cap(my_slice)) } 

输出结果

Slice len = 50 Slice cap = 100

常用操作

通过make定义slice

slice := make([]int, 10)

关于make

在《Effective Go》中的解释为

The built-in function make takes a type T, which must be a slice, map or channel type, optionally followed by a type-specific list of expressions. It returns a value of type T (not *T). The memory is initialized as described in the section on initial values.

对于上述描述的需要理解的是：

• • make主要用于创建切片(slice)，以及我们后面要讲到的Maps和Channel三种类型
• • 返回的值是T，而非*T(即指针T)
• • 内存初始化按照初始值进行

参考资料

• • https://go.dev/doc/effective_go#allocation_make
• • https://dave.cheney.net/2014/08/17/go-has-both-make-and-new-functions-what-gives

截取指定元素

• • 只支持正数，无法像Python一样使用负数反向截取

package main import "fmt" func main() { a := [...]int{1, 2, 3, 4, 5} s1 := a[2:4] fmt.Printf("s1 = %d\n", s1) fmt.Printf("s1 = %v\n", s1) s2 := a[1:5] fmt.Printf("s2 = %v\n", s2) s3 := a[:] fmt.Printf("s3 = %v\n", s3) s4 := a[:4] fmt.Printf("s4 = %v\n", s4) s5 := s2[:] fmt.Printf("s5 = %v\n", s5) s6 := a[2:4:5] fmt.Printf("s6 = %v\n", s6) }

输出结果

s1 = [3 4] s1 = [3 4] s2 = [2 3 4 5] s3 = [1 2 3 4 5] s4 = [1 2 3 4] s5 = [2 3 4 5] s6 = [3 4]

• • slice越界后提示Error: “throw: index out of range”

package main func main() { var array [100]int slice := array[0:99] slice[98] = 1 3 // ERROR: index out of range slice[99] = 2 4 }

Slice扩展(append)

package main import "fmt" func main() { s0 := []int{0, 0} s1 := append(s0, 2) s2 := append(s1, 3, 5, 7) // Append slice instead of value, add ... s3 := append(s2, s0...) fmt.Println("s0 = %v", s0) fmt.Println("s1 = %v", s1) fmt.Println("s2 = %v", s2) fmt.Println("s3 = %v", s3) }

如果追加的是slice，在后面加三个点，普通值直接追加即可

s0 = %v [0 0] s1 = %v [0 0 2] s2 = %v [0 0 2 3 5 7] s3 = %v [0 0 2 3 5 7 0 0]

Slice复制(Copy)

• • slice操作，copy，将源拷贝至目标，并且返回拷贝的数量

copy( destSlice, srcSlice []T) int

package main import "fmt" func main() { var a = [...]int{0, 1, 2, 3, 4, 5, 6, 7} var s = make([]int, 6) fmt.Printf("initial a = %v\n", a) fmt.Printf("initial s = %v\n", s) n1 := copy(s, a[0:]) fmt.Printf("n1 = %v\n", n1) fmt.Printf("a = %v\n", a) fmt.Printf("s = %v\n", s) fmt.Printf("s[2:] = %v\n", s[2:]) n2 := copy(s, s[2:]) fmt.Printf("n2 = %v\n", n2) fmt.Printf("a = %v\n", a) fmt.Printf("s = %v\n", s) }

输出结果

initial a = [0 1 2 3 4 5 6 7] initial s = [0 0 0 0 0 0] n1 = 6 a = [0 1 2 3 4 5 6 7] s = [0 1 2 3 4 5] s[2:] = [2 3 4 5] n2 = 4 a = [0 1 2 3 4 5 6 7] s = [2 3 4 5 4 5]